A diagnostic X-ray imaging system is required to simultaneously have high contrast, high resolution and be fast with low dose to the patient. High contrast and low dose requirements are of a particular interest in mammography, where low contrast tumors and microcalcifications are to be detected at high scatter levels. The limitations of the currently scanning slot systems include the inherently high noise level of the CCD, suboptimal conversion efficiency, limited charge capacity of the CCD and its relatively high scatter fraction (up to 20%) due to its wide scanning slot. The purpose of this project is to develop a scanning multi-slit X-ray imaging system based on an "edge-on" illuminated microchannel plate (MCP) detector for potential application in mammography. The advantages of an "edge-on" MCP detector over other types of X-ray detectors are the possibility to combine high stopping power, superior spatial resolution, direct energy-tocharge conversion, high physical charge amplification and very low noise. More specifically, the aims are: (1) Design and development of a scanning slit X-ray imaging system based on "edge-on" MCP detector and delay line electronics for digital mammography. (2) Investigation of the hypothesis that an X-ray imaging system based on "edge-on" MCP detector can offer substantially improved detection quantum efficiency, resolution, noise and scatter fraction as compared to other currently available mammography systems. (3) Design and development of chip level application specific integrated circuit (ASIC) electronics with very highcount rate capability. (4) Development and evaluation of a clinically applicable single slit prototype X-ray imaging system based on "edge-on" MCP detector with ASIC electronics. (5) Design of a clinically applicable multi-slit x-ray imaging system for digital mammography. The proposed multi-slit X-ray imaging system based on an "edge-on" MCP detector will be photon counting, quantum limited and low scatter fraction. It can potentially provide a high-resolution detector with significant reduction in patient dose for digital mammography.